Research Trends and Accomplishments●Research Trends and Accomplishments

Development of River Environment Evaluation Technologies
Using Remote Sensing, GIS Etc.
ONUMA Katsuhiro (Senior Researcher), FUJITA Koh-ichi (Head)River Environment Division, Environment Department

1. Introduction
In order to manage rivers appropriately, it is essential
to recognize environments that must be preserved andenvironments that must be restored. To do this, we have
performed a census of river environments and prepared riverenvironment information maps, but there is now a growing
need to obtain information related to the environment indetail over wide areas; for example, the networks of waterand greenery at rivers and their surrounding land and themicro-topography that have a great impact on the lives ofplants and animals. Technologies such as laser scanners
and other technologies used to measure micro-topography
over wide areas and classify vegetation using hyperspectral
technology, etc. have progressed in recent years, andat the same time, data bases of numerical national land
digital information, detailed digital information, and otherinformation related to environments are steadily provided by
the Geographical Survey Institute, etc.
The goal of this research is to develop environmental
evaluation and analysis support systems using remotesensing data and GIS (Geographical Information System)
data bases in order to contribute to daily river management
and to make various kinds of plans considering theenvironment; for example, river improvement plans, riverenvironment management plans, and plans for water andgreen networking, and to effectively apply them to conduct
censuses of river environments. The following is an outlineof this research.

Spectral separationby prism and analysis mesh

Spectral separation of lines of light
passing through slits and recording
them with a CCD (Charge Coupled Device)

Figure 1 Vegetation classiﬁ cation using a hyperspectral
sensoris measured by measuring the time taken by a laser pulse
transmitted towards the ground from the aircraft to be
reﬂected back from the ground to the sensor at the sametime as GPS and IMU (Inertial Measurement Unit) are used
to measure the location and the attitude of the aircraft, andthe difference in elevation between them is used to measure
the ground surface elevation. With this method we canmeasure elevation accurately by about ± 15cm.
③ Water quality and water depth
Water quality is surveyed relatively often. For example,
the relationship between the reﬂectivity on water surfaces
measured by hyperspectral sensors and water quality(turbidity, SS (suspended solids), chlorophyll a, etc.) has
been analyzed. Thermal infrared sensors can measureelectro-magnetic waves radiated from the ground surface
in the thermal infrared range, and in recent years, a rise inits spatial resolution has permitted its use to measure riverwater temperature.
Water depth has been measured by laser scanning ofgreen, near-infrared, and Raman scattered light.
⑵ GIS
The two-way exchange of data is now underway as,
for example, vegetation and soil information obtained byremote sensing is used to update geographical information,
and GIS data is used in the process to analyze and evaluate
remote sensing images. For example, the distribution range
of a species of vegetation communities has been estimatedby analyzing GIS vegetation maps obtained by the census
of river environments and spectral images obtained using
aerial hyperspectral sensors.

2. Past use of remote sensing and GIS to evaluate
river environments⑴ Remote sensing
The merit of using remote sensing on aircraft or asatellite lies in their ability to repeatedly obtain surface
data over wide areas . The following are examples of its use
related to river environments.
① Land cover
Vegetation is often classiﬁed using the reﬂectance orluminance of various wave length bands of visual data.
Because sensors with multiple bands including the nearinfrared band are necessary, hyperspectral sensors withmany bands are often used. They are now in regular use tomonitor the state of restoration of vegetation or to learn thedistribution of exotic species. The distribution of riverbed
materials (from sand to gravel) has been estimated byanalyzing pictures taken by high spatial resolution digital
cameras mounted in helicopters.
② Ground surface elevation
The distance between the ground surface and an aircraft
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●Research Trends and Accomplishments
3. Focus of the research
As stated above, remote sensing and GIS have often
been used to analyze each element related to riverenvironments. On the other hand, it is known that there arevarious correlations among these environmental elements;
the frequency of submersion of the river area and vegetationfor example.
The aim of this research is to improve environmental
prediction and evaluation methods by, as shown in Figure
2, combining these ﬁndings and making the best possible
use of the characteristics of remote sensing, spatial
analysis functions of GIS (overlay, buffering, etc.) and their
good correlation with various analytical, prediction, andevaluation models to clarify environmental elements and themechanisms of their interrelationships.
For example, when we obtain wide area data concerning
river shape and soil distribution that have big impacts on thegrowth and life of plants and animals by using aerial laser
measurements and other remote sensing techniques, oranalyze the interrelationships between those data and thedistributions of plants and animals by using GIS data; forexample, river environmental information maps, and analyze
and predict the changes of river shape caused by the changeof river ﬂow volumes and quantity of supplied sediment fromdams, it will probably also be possible to predict the impactsof dams on plants and animals.

a). This was done on the Ara River, Tama River, and theNakatsu River (Sagami River System). At the same time, wemeasured water quality etc on site. Using these data and theresults of past surveys of lateral river measurements, riverenvironment information maps, and other related surveys
to environments, we will evaluate the various environmentalelements. And using these data we will analyze correlationsof vegetation with submersion frequency distribution (basedon ground elevation data etc. obtained by laser scanners) orwith grain size distribution. On the Nakatsu River that was
one of the districts studied, and the location of the Miyagase
Dam, through this research we will try to apply the method
using remote sensing to predict and evaluate the various
impacts of a dam on river environments.
⑵ Future plans
Based on the achievements of 2003, we are scheduled toapply remote sensing and GIS to develop an environmental
evaluation and analysis support system, and improve thesystem through applying it in the ﬁeld. For example, using
remote sensing and existing GIS data, we may develop thesystem to evaluate the diverse of vegetation and continuityof greenery and analyze the correlation between theseresults and animal distribution. And we are scheduled toevaluate and analyze environments including areas aroundrivers using existing data such as the results of basic
surveys of natural environment conservation provided by
the Ministry of the Environment. And ﬁnally, we aim todevelop the river environment prediction system that applies
remote sensing and GIS described in 3. The fruits of thisresearch are expected to apply to various kinds of planningand daily management as explained in 1. Introduction.
We will conduct a study to prepare a guideline for riverenvironmental evaluations using remote sensing and GIS,
which can be utilized by construction ofﬁces in the ﬁeld.

4. Content of the research⑴ Present efforts
In 2003 that was the ﬁrst year of the research, using
laser scanners, hyperspectral sensors, thermal infraredsensors, and three-line sensors we made aerial surveys
to measure and analyze ground elevation, tree height,
soil grain size distribution, land cover classiﬁcation, andwater quality (water temperature, turbidity, chlorophyll

Existing GIS data or the resultsof past surveys converted to GIS data

Use of remote sensing data
Improving data precisionObtaining wider area data
Obtaining data including regional
characteristics, simultaneity, andcyclic properties etc. (only satellites)
Identification of new environmental
elements

Detailed
digital information
National land
digital information
River environment
information maps

Basic environment
Water temperature
Water quality
River shape
Soil distribution etc.
Flow volume
Sediment supply

State of growth and habitationof plants and animals
Growth and habitation

Human impacts

River environment

Animals
PlantsFood chain, competition and coexistence

Using remote sensing and GIS to clarify environmental elements
and their interrelationship mechanisms

Improving prediction and evaluation methods
Supporting plan enactment and daily management

Figure 2 Overall image of the research

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